Ubuntu 14.04 LTS (Trusty Tahr) released and its time to upgrade

Ubuntu 14.04 LTS
Ubuntu 14.04, codenamed Trusty Tahr has been just released a few hours ago and its time to upgrade to get the latest Ubuntu. Its the first release of this year and is an long term release that shall get support till April 2019. To learn about what's new in 14.04 check out the release notes.
Ubuntu 13.10 and 12.04 LTS users should be able to safely upgrade to 14.04 LTS throught the the update-manager. For other versions, the recommended way is to re-install Ubuntu.
Upgrade Ubuntu on desktop
The steps to upgrade Ubuntu on the desktop are quite simple. First update your package cache and all packages using apt, and then use update-manager to upgrade to the next version of the Ubuntu.
1. Upgrade all packages
$ sudo apt-get update
$ sudo apt-get upgrade
If you get a message that "The following packages have been kept back" then you need to run apt-get with dist-upgrade to upgrade all packages.
$ sudo apt-get dist-upgrade
If the linux kernel is upgraded in the process, then you would have to restart the machine before proceeding.
2. Disable any failed PPA repositories
While doing apt-get update, if apt fails to download repository information for any ppa, then disable those ppas before continuing to...